In labor intensive, cost sensitive businesses such as the automobile aftermarket time savings such as rapid cure or cure on demand coatings are premium benefits. In addition, there is an intense effort by researchers and the industry to provide high and 100% solids formulations to reduce the use of solvents for user health and environmental reasons.
Current body putties (sometimes included in the term "body fillers") are based on unsaturated polyester resins which are cured by a free radical curing mechanism initiated by organic peroxides. Drying times to allow sanding take 20-30 minutes. This delays the repair process and is especially inefficient if needed repairs are noticed in the paint booth where delays seriously impact shop productivity.
Radiation curable compositions containing carbon--carbon (C--C) unsaturated monomers and polythiols were developed in the early 1970s. U.S. Pat. No. 4,234,676 describes a composition comprising a C--C unsaturated polymer, a cross linkable monomer, a polythiol, and curing agent directed primarily at printing plate production.
U.S. Pat. No. 4,808,638 (Steinkraus, et al) describes a composition comprising a norbornene resin, polythiol, and free radical initiator which can be photocured in visible light when a iron arene complex is present.
U.S. Pat. No. 4,139,385 (Crivello) describes a composition comprising a polyolefin, polythiol, and onium salt photoinitiator. The films, 75 micrometers, (3 mil) thick were curable by a cationic mechanism with UV light as an initiator.